1. Field of the Invention
The present invention relates to a novel method of making magnetic recording heads, especially of those for use with a very narrow recording track.
2. Prior Arts
Progress in the technology of magnetic recording in recent years is remarkable; especially in the technology of attaining higher recording density by narrowing recording track width. For example, during the last ten years, the track pitch of a magnetic recording head for video recording has been narrowed by a factor of 10, resulting in heads having a track pitch of under 20 .mu.m. Corresponding to such narrowing of the track pitch, the tolerance requirements of recording head such as used in a video tape recorder or the like has become particularly strict; for example, .+-.2 .mu.m or higher accuracy is required.
Conventional video tape recorder heads have typically been made by a method which will be hereafter described with reference to FIGS. 1(a), 1(b), 1(c), 1(d) and 2.
First, a pair of ferromagnetic substance core blocks 1 and 1' shown in FIG. 1(a) are prepared. And then, partial grooves 2, 2 . . . are formed; thereon by a known method such as by using a cutter or dicing saw. Grooves 2, 2 . . . define track width.
A non-magnetic substance 3, such as glass, is then filled in the partial grooves 2, 2 . . . as shown by FIG. 1(c), and mirror-grinding is carried out for abutting faces, and subsequently, a gap spacer film 4 is applied at least on one of the abutting faces. Also a winding groove 102 is formed by known cutting or dicing methods on either block 1 or 1'.
Thereafter, the half blocks 1 and 1' are assembled and bonded such that the faces abut together as shown in FIG. 1(d), by means of bonds 5, 5 such as low melting point glass. Then the assembled body is cut into individual units at the dividing faces shown by dotted lines in FIG. 1(d). The magnetic cores of the conventional magnetic head, as shown in plan view in FIG. 2 are manufactured. Then a winding (not shown) is wound through the winding groove 102.
Since the above-mentioned conventional method uses the mechanical step of dicing or grinding to form the partial grooves 2, 2 . . . , the upper limit of the accuracy is limited by that of the mechanical technique. The accuracy of mechanical tooling techniques is considered to have come almost to a practical limit, and therefore, it has been difficult to obtain a dimensional accuracy of .+-.1 .mu.m. And such dimensional limit has determined accuracy limit of the conventional method. If the accuracy limit is intended to be obtained in such method, extremely strict controls of temperature, moisture, and so on are required, and such is not practical in actual mass production level.
As a result of the above-mentioned circumstance, photolithographic etching methods have recently begun to be utilized in manufacturing narrow track pitch magnetic recording heads. However, conventional photolithographic etching methods are not sufficient, and it is not yet easy to attain both accuracy and deep engraving at the same time. Further, it is still very difficult to attain .+-.1 .mu.m accuracy, using the photolithographic etching done.